Notes on the WJ-5008 YIG
Oscillator

I wanted to take some high frequency measurements, so bought some
Watkins Johnson YIG oscillatorsand filters very cheaply on EBay.
The WJ-5008 dates back to the early 1970's.

Unfortunately very
little data was available on the net regarding the use of this
device.

Spectral characteristics and coil sensitivity as well
as a full theoretical description are hereand
here
The coil measured 12 ohm, so from the date the inductance is about
0.2 Henry, and the sensitivity should be about 25 Mhz/ma.

No
pinouts etc were available.

I tried simply putting power to it
(17 volt shown printed) with no result.

Next step was to pull
it apart. It contained a PNP darlington, a TC thermistor, and a
reverse connected schottkydiode for protection. The Gunn diode is
mounted between two massive heat sinks.

After
resoldering a broken lead and biasing the magnet to about 8 gHz (it
has no permanent bias magnet)it sprang into life. It needs about
0.4 amps diode supply current - giving a wallplate efficiency <<
0.1% !

More modern oscillators use FET or BJT oscillators and
need far less power, and some provide a much widertuning
range.It's still a very creditable performance considering it's
nearly 40 year old, and it must have been a pace-setter when it was
introduced.These devices were used in various sorts of now
obsolete aircraft radar scanners and jammers, which is probablywhy
user data is not readily available, and also why they available very
cheaply.

It looks like a number of other WJ YIG oscillators
have similar pinouts

I might also post some data on the
WJ-643-21 four stage tuned filters at some stage.